Systems, devices and methods for wireless transmission of signals through a faraday cage

ABSTRACT

Embodiments of the present disclosure provide devices and systems that support wireless communication between wireless communication devices residing within, and external to, a Faraday cage. In some embodiments, devices and systems are provided for transmitting wireless signals through a waveguide port of a Faraday cage for wireless signals having frequencies below the cutoff frequency of the waveguide port, where a portion of the waveguide port is compromised by the presence of a conductor, thereby permitting the propagation of electromagnetic waves. In some embodiments, aspects of the present disclosure are employed to adapt a magnetic resonance imaging system for communications between a scanner room and a control room.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase application claiming the benefit ofthe international PCT Patent Application No. PCT/CA2016/051417, filed onDec. 2, 2016, in English, which claims priority to U.S. ProvisionalApplication No. 62/262,803, titled “SYSTEMS, DEVICES AND METHODS FORWIRELESS TRANSMISSION OF SIGNALS THROUGH A FARADAY CAGE” and filed onDec. 3, 2015, the entire contents of which are incorporated herein byreference.

BACKGROUND

The present disclosure relates to electromagnetically shieldedenvironments. More particularly, the present disclosure relates tomagnetic resonance imaging systems.

The use of magnetic resonance (MR) imaging has expanded from diagnosticimaging to include the guidance of a variety of interventions. Theseinclude, MR-guided biopsies, and ablation therapies performed by bothradiofrequency (RF) energy and high-intensity focused ultrasound.

Many diagnostic and interventional procedures require or are aided bythe presence of a clinician, staff or family members inside the Faradaycage. The purpose of the Faraday cage is to block any electromagneticenergy within the operating bandwidth of the MR scanner (typically 64MHz+/−250 kHz for a 1.5 T system and 128 MHz+/−250 kHz for a 3 Tsystem). This eliminates outside interference with the scanner andpreserves image quality.

It is often desirable for people inside the Faraday cage to communicatewith people outside of the Faraday cage; this is particularly true inthe case of interventional procedures. In addition to the need forcommunication, peripheral devices that enable the visualization ofimages and the interactive control of the MR scanner are also desirable.

Currently, there are wired solutions that enable communication betweenthe control room and the scanner room, however, the presence of wires ineither room attached to individuals can be very cumbersome, especiallywhen a clinical procedure is taking place and people are required tomove around the room. Communication with someone inside a scanner roomis further hindered by the loud noises generated by the MR scanner.

Wireless technologies are beneficial in that they reduce the cluttercaused by numerous wired peripheral devices. In an MR suite, however,wireless signals originating from inside the scan room are unable toreach the adjacent control room due to the Faraday cage. Similarly, theFaraday cage also prevents wireless signals originating from the controlroom to propagate into the scanning room.

SUMMARY

Embodiments of the present disclosure provide devices and systems thatsupport wireless communication between wireless communication devicesresiding within, and external to, a Faraday cage. In some embodiments,devices and systems are provided for transmitting wireless signalsthrough a waveguide port of a Faraday cage for wireless signals havingfrequencies below the cutoff frequency of the waveguide port, where aportion of the waveguide port is compromised by the presence of aconductor, thereby permitting the propagation of electromagnetic waves.In some embodiments, aspects of the present disclosure are employed toadapt a magnetic resonance imaging system for communications between ascanner room and a control room.

In a first aspect, there is provided a wireless communication system forcommunicating through a waveguide port of a Faraday cage, the wirelesscommunications system comprising:

one or more internal wireless communication devices located within theFaraday cage, and one or more external wireless communication deviceslocated external to the Faraday cage, wherein said one or more internalwireless communication devices and said one or more external wirelesscommunication devices are configured for wireless communication within afrequency band that lies, at least in part, below a cutoff frequency ofsaid waveguide port; and

a wireless bridge device comprising an antenna and a transceiveroperably connected to said antenna, wherein at least a portion of saidwireless bridge device is housed within said waveguide port, such thatsaid antenna resides within said waveguide port;

wherein a conductive path is provided within a first longitudinalportion of said waveguide port, wherein said first longitudinal portionextends between a first side of said waveguide port and an intermediatelocation within said waveguide port, and wherein said conductive path isunshielded and resides within said first longitudinal portion withoutmaking electrical contact with said Faraday cage, such that thepropagation of electromagnetic waves is supported within said firstlongitudinal portion of said waveguide port, and

wherein a second longitudinal portion of said waveguide port is absentof said conductive path, said second longitudinal portion extendingbetween said intermediate location and a second side of said waveguideport, such that electromagnetic waves having a frequency below thecutoff frequency are attenuated within said second longitudinal portion,thereby preserving the functionality of said waveguide port as ahigh-pass filter; and

wherein said antenna resides within said waveguide port at an antennalocation that is sufficiently close to said second side of saidwaveguide port to support the transmission and reception of wirelesssignals to and from said one or more internal wireless communicationdevices, and wherein said first longitudinal portion is of sufficientlength to support the transmission and reception of wireless signals toand from said one or more external wireless communications devices.

In another aspect, there is provided a wireless communication system forcommunicating through a waveguide port of a Faraday cage, the wirelesscommunications system comprising:

one or more internal wireless communication devices located within theFaraday cage, and one or more external wireless communication deviceslocated external to the Faraday cage, wherein said one or more internalwireless communication devices and said one or more external wirelesscommunication devices are configured for wireless communication within afrequency band that lies above a cutoff frequency of said waveguideport; and

a wireless bridge device comprising an antenna and a transceiveroperably connected to said antenna, wherein at least a portion of saidwireless bridge device is housed within said waveguide port, such thatsaid antenna resides within said waveguide port;

wherein said antenna resides within said waveguide port at an antennalocation that is suitable for to support the transmission and receptionof wireless signals to and from said one or more internal wirelesscommunication devices and to and from said one or more external wirelesscommunications devices.

In another aspect, there is provided a wireless communication system forcommunicating through a waveguide port of a Faraday cage, the wirelesscommunications system comprising:

one or more internal wireless communication devices located within theFaraday cage, and one or more external wireless communication deviceslocated external to the Faraday cage; and

a wireless bridge device comprising an antenna and a transceiveroperably connected to said antenna, wherein at least a portion of saidwireless bridge device is housed within said waveguide port, such thatsaid antenna resides within said waveguide port;

wherein a conductive path is provided within a first longitudinalportion of said waveguide port, wherein said first longitudinal portionextends between a first side of said waveguide port and an intermediatelocation within said waveguide port, and wherein said conductive path isunshielded and resides within said first longitudinal portion withoutmaking electrical contact with said Faraday cage, such that thepropagation of electromagnetic waves is supported within said firstlongitudinal portion of said waveguide port, and

wherein a second longitudinal portion of said waveguide port is absentof said conductive path, said second longitudinal portion extendingbetween said intermediate location and a second side of said waveguideport, such that electromagnetic waves having a frequency below a cutofffrequency of said waveguide port are attenuated within said secondlongitudinal portion, thereby preserving the functionality of saidwaveguide port as a high-pass filter; and

wherein said antenna resides within said waveguide port at an antennalocation that is sufficiently close to said second side of saidwaveguide port to support the transmission and reception of wirelesssignals to and from said one or more internal wireless communicationdevices, and wherein said first longitudinal portion is of sufficientlylength to support the transmission and reception of wireless signals toand from said one or more external wireless communications devices.

A further understanding of the functional and advantageous aspects ofthe disclosure can be realized by reference to the following detaileddescription and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the drawings, in which:

FIG. 1 is a schematic diagram of a typical magnetic resonance imagingsuite, comprising a magnetic resonance imaging scanner, magnet(scanning) room, control room, Faraday cage, and a waveguide port.

FIG. 2 is an illustration of an example system including a wirelessbridge device housed within a waveguide port, in which a longitudinalportion of the waveguide port is compromised by the presence of aconductive path, such that the propagation of electromagnetic wavesbelow the cutoff frequency of the waveguide is possible within thecompromised portion, while the remainder of the waveguide attenuates thepropagation of electromagnetic waves having a frequency below the cutofffrequency.

FIGS. 3A and 3B show example embodiments for the positioning of theantenna relative to the compromised portion of the waveguide port.

FIGS. 4A-4F illustrate various example embodiments in which a conductivefeature is employed to provide a conductive path over a portion of thewaveguide port.

FIG. 5A illustrates the components of an example wireless bridge device.

FIG. 5B illustrates an example audio communications device.

DETAILED DESCRIPTION

Various embodiments and aspects of the disclosure will be described withreference to details discussed below. The following description anddrawings are illustrative of the disclosure and are not to be construedas limiting the disclosure. Numerous specific details are described toprovide a thorough understanding of various embodiments of the presentdisclosure. However, in certain instances, well-known or conventionaldetails are not described in order to provide a concise discussion ofembodiments of the present disclosure.

As used herein, the terms “comprises” and “comprising” are to beconstrued as being inclusive and open ended, and not exclusive.Specifically, when used in the specification and claims, the terms“comprises” and “comprising” and variations thereof mean the specifiedfeatures, steps or components are included. These terms are not to beinterpreted to exclude the presence of other features, steps orcomponents.

As used herein, the term “exemplary” means “serving as an example,instance, or illustration,” and should not be construed as preferred oradvantageous over other configurations disclosed herein.

As used herein, the terms “about” and “approximately” are meant to covervariations that may exist in the upper and lower limits of the ranges ofvalues, such as variations in properties, parameters, and dimensions.Unless otherwise specified, the terms “about” and “approximately” meanplus or minus 25 percent or less.

It is to be understood that unless otherwise specified, any specifiedrange or group is as a shorthand way of referring to each and everymember of a range or group individually, as well as each and everypossible sub-range or sub-group encompassed therein and similarly withrespect to any sub-ranges or sub-groups therein. Unless otherwisespecified, the present disclosure relates to and explicitly incorporateseach and every specific member and combination of sub-ranges orsub-groups.

As used herein, the term “on the order of”, when used in conjunctionwith a quantity or parameter, refers to a range spanning approximatelyone tenth to ten times the stated quantity or parameter.

Unless defined otherwise, all technical and scientific terms used hereinare intended to have the same meaning as commonly understood to one ofordinary skill in the art. Unless otherwise indicated, such as throughcontext, as used herein, the following terms are intended to have thefollowing meanings:

As used herein, the phrase “Faraday cage” refers to an enclosure formedfrom a conductive material, such that electromagnetic waves areprevented from passing into or out the enclosed volume. In someembodiments, a Faraday cage may be formed from a solid conductivematerial, while in other embodiments, a Faraday cage may be formed froma conductive mesh. A “Faraday cage” may also be referred to as a“Faraday shield” or a “Faraday screen”.

As used herein, the terms “waveguide port” and “waveguide channel”refers to a hollow conductive structure penetrating a Faraday cage,where the hollow conductive structure is configured to act as ahigh-pass filter. In some embodiments, the waveguide port may have asize that is suitable for moving items into or out of a Faraday cage.

As used herein, the phrases “in electrical contact” and “in electricalcommunication” refer to two or more conductors having substantially thesame electrical potential due to direct or indirect electrical contactbetween the conductors.

Embodiments of the present disclosure provide devices and systems thatsupport wireless communication between wireless communication devicesresiding within, and external to, a Faraday cage. In some embodiments,devices and systems are provided for transmitting wireless signalsthrough a waveguide port of a Faraday cage for wireless signals havingfrequencies below the cutoff frequency of the waveguide port. In someembodiments, aspects of the present disclosure are employed to adapt amagnetic resonance imaging system for communications between a magnet(scanner) room and a control room.

With reference to FIG. 1, a conventional magnetic resonance system isillustrated. MR scanner 100 is situated in magnet (scanner) room 110,which is surrounded by a Faraday cage 105. Faraday cage 105 is anenclosure formed with conducting material (either in solid or meshform). Such an enclosure attenuates ambient RF signals and prevents themfrom entering the MR scanner room. Faraday cage 105 is often locatedwithin the walls and windows of MR scanner room 110. Much of thecontrolling and operation of MR scanner 100 occurs in adjacent controlroom 115.

As shown in FIG. 1, a waveguide port 120 is provided within Faraday cage105. Waveguide port 120 is a conductive passage that is electricallyconnected to Faraday cage 105, and forms an opening through Faraday cage105. Waveguide port 120 has dimensions that are selected such it acts asa high pass filter to electromagnetic waves, with a cutoff frequencywell above the operational frequency of MR scanner 100. As a result, MRimage quality is not compromised by the presence of waveguide port 120.Waveguide port 120 may be employed, for example, to permit the passageof non-conductive materials, such as anaesthesia tubes, between scannerroom 110 and control room 115. In one non-limiting embodiment, anexample waveguide port may be a substantially cylindrical tube, formedfrom a conductive material, with a diameter of approximately 10 cm and alength of approximately 30 cm.

For any conducting hollow guide, including those that are circular orrectangular in cross section, the electric potential of the interior ofthe conductor is a constant. The consequence of this is that, accordingto the wave equation, the only electromagnetic propagation modes thatare able to exist are the transverse magnetic (TM) or transverseelectric (TE) modes. Both of these propagation modes have distinctcutoff frequencies whereby only electromagnetic waves above the cutofffrequency are able to propagate through the hollow guide.

The problems associated with the transmission of electrical signalsthrough a waveguide port are described in Patent Cooperation TreatyPatent Application No. PCT/CA2014/050086, titled “SYSTEMS, DEVICES ANDMETHODS FOR TRANSMITTING ELECTRICAL SIGNALS THROUGH A FARADAY CAGE”. Thevarious embodiments of Patent Cooperation Treaty Patent Application No.PCT/CA2014/050086 involve the use of a wired signal path within thewaveguide port, while preserve the operation of the waveguide port as ahigh-pass filter by ensuring that an unscreened conductors residingwithin the waveguide port are in electrical communication with thewaveguide port.

Specifically, Patent Cooperation Treaty Patent Application No.PCT/CA2014/050086 teaches that “in order to pass a conductor through thehollow guide while maintaining the inability for TEM propagation modesto exist, it is necessary for conductors in the waveguide to be at thesame potential as the interior surface of the hollow guide (i.e. beequipotential with the interior surface of the hollow guide).” PatentCooperation Treaty Patent Application No. PCT/CA2014/050086 thereforeteaches that a wired signal path is required for an electrical signal totraverse the waveguide port, where the wired signal path is shielded byan outer conductor that is in electrical communication with thewaveguide port. The electrical contact of the outer conductor maintainsthe operation of the open portion of the waveguide as a high passfilter.

Many of the example embodiments disclosed by Patent Cooperation TreatyPatent Application No. PCT/CA2014/050086 may be disadvantageous in thatwired connections for delivering signals across the waveguide port arerequired on at least one side of the waveguide insert. Only theembodiment shown in FIG. 16 of Patent Cooperation Treaty PatentApplication No. PCT/CA2014/050086 discloses a wireless device thatavoids the need for a wired connection from the magnet room or thecontrol room. Unfortunately, such a device is costly and complex, asseparate antennas are required on both sides of the waveguide port, andwhere the electrical signal traverses the waveguide port over a wirethat is shielded by an outer conductor, where the outer conductor is inelectrical contact with the waveguide port.

The present inventors therefore endeavored to address this problem inorder to provide a solution that was less costly, less complex, and didnot require the use of a grounded waveguide insert in order to achievesignal transmission at frequencies below the cutoff frequency of thewaveguide port. Accordingly, in contrast to the teachings of PatentCooperation Treaty Patent Application No. PCT/CA2014/050086, variousexample embodiments of the present disclosure provide wirelesscommunication systems that do not require separate antennas on each sideof the waveguide port for wireless operation, do not require the use ofa shielded conductive path for the electrical signal to traverse thewaveguide port, and instead employ the use of an internal conductivepath to partially compromise the waveguide in order to support thepropagation of electromagnetic waves within a longitudinal portion ofthe waveguide port.

Referring now to FIG. 2A, an example system is shown for enablingwireless communication through a waveguide port of a Faraday cage. Inthis example system, a wireless bridge device 150 is provided tofacilitate communication between one or more internal wireless audiocommunications devices 125A-B that reside within the Faraday cage 105and one or more external wireless audio communications devices 125C-D.The wireless audio communications devices 125A-D transmit and receivewireless signals in order to communicate audio signals therebetween, andthe wireless bridge device 150 is employed to receive the variouswireless signals from the internal and external wireless communicationsdevices 125A-D, perform optional signal routing and mixing, andrebroadcast the audio signals into both the magnet room 110 and thecontrol room 115, acting as a wireless bridge between the wirelesscommunications devices inside and out of the Faraday cage 105. Thewireless broadcast device 150 is shown including at least one antenna130, at least one radio transceiver 140, one or more optional additionalelectronic components 145, and a power source or power connector 155.The wireless broadcast device 150 is housed, at least partially, withinthe waveguide port 120, such that the antenna 130 resides within thewaveguide port 120.

As shown in the figure, the antenna 130 of the wireless broadcast device150 is located within the waveguide port 120 at a location that issufficient close to the magnet room 110 to support the transmission andreception of wireless signals to and from the internal wirelesscommunications devices 125A-B, even though this portion of the waveguideport, shown as uncompromised longitudinal portion 170, acts as ahigh-pass filter causes some attenuation of the propagation ofelectromagnetic waves. If the antenna 130 is located sufficiently closeto the magnet room side of the waveguide port 120, the attenuation willbe sufficiently low that the transmission and reception of wirelesssignals to and from the internal wireless communication devices will befeasible.

For example, many circular waveguides used in magnetic resonance systemshave a diameter of 2 inches. The cutoff frequency that corresponds tothis diameter is 3.46 GHz, which prevents the propagation, within thewaveguide, of wireless signals having frequencies in the 2.4-2.5 GHzrange. However, if the antenna 130 is located sufficiently close to themagnet room side of the waveguide port, electromagnetic waves will beable to propagate from the magnet room to the antenna, and from theantenna to the magnet room, without appreciable attenuation, therebysupporting wireless communication between the internal communicationdevices 125A-B and the antenna 130. For example, in the case ofwaveguides having a diameter of two inches, it has been found thatsignal transmission and reception for frequencies in the 2.4-2.5 GHzrange is feasible when the antenna is positioned within 5 centimeters ofthe magnet room side of the waveguide port.

The positioning of the antenna 130 relative to the magnet room side ofthe waveguide port supports wireless transmission and reception betweenthe internal wireless communications devices 125A-B and the wirelessbroadcast device 150, but does not alone facilitate the transmission andreception of wireless signals from the external wireless communicationsdevice 125C-D to and from the antenna 130. As shown in the exampleembodiment illustrated in FIG. 2A, in order to facilitate thetransmission and reception of wireless signals from the externalwireless communications device 125C-D to and from the antenna 130, alongitudinal portion of the waveguide 180 is compromised (breached) bythe presence of an unshielded conductive path that resides within thewaveguide port 120 without making electrical contact with the waveguideport or Faraday cage. The presence of the conductive path supports orpermits (e.g. via the presence of additional modes) the propagation ofelectromagnetic waves within waveguide port 120. The extent of theconductive path (and thus the longitudinal portion 180) is select toenable the transmission and reception of wireless signals to and fromthe external communications device 125C-D to the antenna 130. In someembodiments, the electrical conductive path is continuous within thecompromised longitudinal portion of the waveguide. The electricallyconductive path that causes the longitudinal portion of the waveguideport to be compromised to allow the propagation of electromagnetic wavescan take on many different forms, and several non-limiting examples areprovided below.

According to the example embodiment described above, the antenna 130resides within the waveguide port at a location that is sufficientlyclose to the magnet room side of the waveguide port to support thetransmission and reception of wireless signals to and from the internalwireless communication devices, and the compromised longitudinal portionof the waveguide port is of sufficiently length to support thetransmission and reception of wireless signals to and from the externalwireless communications devices. The sufficiency of the proximity of theantenna to the magnet room side of the waveguide port, and thesufficiency of the length of the compromised longitudinal portion, maybe determined according to several different criteria. It will beunderstood that the criteria may depend on aspects of the system such asthe diameter and length of the waveguide port, the wireless frequencies,the transmitted power of the wireless signals, and the sensitivity ofthe transceivers.

For example, the sufficiency may be determined based on thesignal-to-noise ratio of the wireless signals that are received by thewireless bridge device and/or the wireless communication devices. Insome example implementations, the proximity of the antenna to the magnetroom side of the waveguide port, and the length of the compromisedlongitudinal portion, may be selected to provide a signal-to-noise ratioof at least 1 dB, at least 2 dB, at least 3 dB, or more.

According to another example, the sufficiency may be determined based onthe propagation loss, within the waveguide port, experienced by thewireless signals that are received by the wireless bridge device and/orthe wireless communication devices. In some example implementations, theproximity of the antenna to the magnet room side of the waveguide port,and the length of the compromised longitudinal portion, may be selectedsuch that the signal loss due propagation within the waveguide port isless than 1 dB, less than 2 dB, less than 3 dB, less than 5 dB, or lessthan 10 dB.

FIGS. 3A and 3B illustrate two example embodiments with differentlocations of the antenna 130 relative to the compromised longitudinalportion 180 of the waveguide port 120, where the compromised portion 180is shown including unshielded conductor 160 that is free from electricalcontact with the waveguide port 120. In FIG. 3A, the antenna is locatedwithin the uncompromised longitudinal portion 170 of the waveguide port,while FIG. 3B illustrates an alternative example embodiment in which theantenna 130 is located within the compromised longitudinal portion 180of the waveguide port.

The configuration shown in FIG. 3A may be advantageous in that thewireless signals transmitted to or received from the magnet room side ofthe waveguide, and wireless signals transmitted to or received from thecontrol room side of the waveguide, each traverse a shorter length ofthe uncompromised portion 170 of the waveguide than electromagneticwaves that travel through the entire length of the waveguide port.Therefore, the propagation loss associated with electromagnetic noisetraversing the waveguide port exceeds the propagation loss of wirelesssignals transmitted or received by the wireless bridge device. In oneexample embodiment, the antenna 130 is located at or near the center ofthe uncompromised waveguide portion 170 (e.g. offset from center of theuncompromised longitudinal portion 170 by an amount less than 5%, 10%,15%, 20% or 25% of length of the uncompromised longitudinal portion170).

Referring now to FIGS. 4A-4F, several different example implementationsare illustrated for compromising a longitudinal portion of the waveguideto support the propagation of electromagnetic waves. Without intendingto be limited by theory, it is believed that the propagation ofelectromagnetic waves within the compromised portion of the waveguideport will be most efficient when the waveguide port and the conductormost resemble a coaxial configuration (e.g. such as in the case of acoaxial cable) where the conductor is located in, or near to the axialcenter of the waveguide (e.g. offset from the axial center of thewaveguide by an amount less than 5%, 10%, 15%, 20% or 25% of waveguidediameter). An example implementation of such a configuration is shown inFIG. 4A, where conductor 160A is centrally located within the waveguideport 120. FIG. 4B illustrates an alternative implementation in which aplanar (e.g. flat, rectangular) conductor is provided within thewaveguide port.

While FIGS. 4A and 4B illustrate the use of additional conductors thatare provided in addition to the wireless bridge device (which is itselfnot shown in the figures), FIG. 4C shows an alternative exampleimplementation in which the housing 150A of the wireless bridge deviceis formed from a non-conductive material, and where a conductive segment160A (e.g. a wire, planar metallic strip, or foil) is located on thehousing 150A, such that the conductive segment 160C does notelectrically contact the waveguide port 120. Examples of a conductivestrip include, but are not limited to, a rectangular piece of coppertape or other conductive tape. The strip may also consist of a rigidpiece of copper or other conductive material affixed to the enclosure.Examples of other types of conductive materials include but are notlimited to wires and cables. The conductive material could be affixed tothe bottom face of the enclosure, as illustrated, or on any of the otheroutside faces. Alternatively, one or more conductive strips could beplaced on any inside surface of the waveguide enclosure.

FIG. 4D illustrates an alternative example embodiment in which thehousing 150B is electrically conductive and compromises the waveguideport 120, while remaining free from electrical contact with thewaveguide port 120 due to the presence of dielectric spacers 162 and164. The dielectric (insulating) material may consist, for example, ofany material affixed to the enclosure that is non-conductive. Thedielectric material may be placed at locations where the housing of thewireless bridge device would touch the inner surface of the waveguide ina typical operating configuration. Examples of non-conductive materialsinclude but are not limited to electrical tape, polyimide (Kapton) tape,plastics, or epoxy layers.

FIG. 4E illustrates another example embodiment showing an irregularlyshaped housing 150D, while FIG. 4F illustrates an example embodiment inwhich the perimeter of the housing 150E is coated or otherwise enclosedby a dielectric material 166.

In other example implementations, one or more unshielded conductorsprovided within the wireless bridge device 150 may be suitable forcompromising the waveguide to allow the propagation of electromagneticwaves. For example, a planar conductive layer in a printed circuit boardwithin the wireless bridge device may be sufficient to compromise thewaveguide, provided that the waveguide housing is not formed from amaterial that electrically shields the internal circuit board.

In some example embodiments, the wireless broadcast device 150 maywirelessly communicate with a communications control device 190, whichmay reside within the Faraday cage, or external to the Faraday cage. Anexample implementation is shown in FIG. 2A, where a communicationscontrol device 190 is shown residing within the control room.Communications control device 190 may include a wireless transceiver andantenna for supporting wireless communications with the wirelessbroadcast device 150. Communications control device 190 may alsoinclude, for example, a processor, a memory, a display, and one or moreinput devices (which may be a touch screen of the display) rendering auser interface that enables a user to configure and/or control, andoptionally monitor, parameters of the communications system. In someexample implementations, communications control device 190 mayoptionally performing signal routing, mixing, or other signalprocessing, in addition or in alternative to the signal processingperformed by the wireless bridge device 130.

FIG. 5A is a block diagram showing the components of an exampleimplementation of the wireless communications device 150, which includesan antenna 130 in electrical communication with a wireless transceiver140, where the wireless transceiver 140 is operably connected to arouting processor 146 that performs audio routing and audio mixing. Apower source of power connector 155 is also provided to deliver power tothe various electronic components.

Although FIG. 5A illustrates an example implementation with a singletransceiver 140, other example implementations may employ multipletransceivers that operate at different frequencies to supportmultiplexed communication. Furthermore, although FIG. 5A illustrates anexample implementation with a single antenna 130, other exampleimplementations may employ multiple antennas that are configured tooperate at different frequencies to support multiplexed communication.In one example embodiment, a plurality of antennas may be provided,where each antenna is connected to a separate transceiver.

In one example implementation, the communication of each wirelesscommunication device with the other wireless communication devices isdetermined by a routing processor 146 housed inside the wireless bridgedevice. The wireless signals transmitted from each wirelesscommunication device are received by the wireless bridge device via anarray of N transceivers, where N is greater than or equal to 1. Atransceiver is able to communicate with multiple wireless communicationdevices by ensuring that the wireless signals received from the variouswireless communication devices are re-broadcasted to their respectivetargets. In the present example implementation, this is achieved using amethod known as frequency hopping. The transceiver array in the wirelessbridge device constantly receives transmissions over the air, sorts themaccording to their wireless communication device sources, and relays thesignals through independent channels to the routing processor. Therouting processor determines what to send back to each wirelesscommunications device and outputs the signals in independent channelsback to the transceiver array. For example, in an example intercomconfiguration, the signals received from a given wireless communicationdevice are routed such that they are re-broadcasted to every wirelesscommunications device other than itself. The transceiver array thereforeencodes and re-broadcasts transmissions for the various wirelesscommunications devices. Each wireless communication device employs itsrespective transceiver to decode the signals and determines its inputsignal.

In one example method, an assigned transmission band is divided intosub-bands. A paired transmitter/receiver follows a unique sub-bandhopping pattern over time to communicate. This way, an over the airbroadcast in the assigned frequency band can carry transmission formultiple receivers, each operating with different sub-band hoppingpatterns.

It will be understood that many different types of wireless protocolsmay be employed to encode and wirelessly transit signals. For example,one commonly used wireless protocol is the Bluetooth protocol. In atypical use, a Bluetooth master transceiver is paired to one or moreslave transceivers. Wireless data is passed between the transceiversusing digital packets. Bluetooth transmissions span the frequency bandbetween 2402 and 2480 MHz. Bluetooth divides this band into 79 1-MHzsub-bands, and Bluetooth transmitters usually perform 1600 sub-band hopsper second. Bluetooth is only one example of a wireless protocols.Others include, but are not limited to, Wi-Fi (802.11) and ZigBee(802.15.4).

An example of implementation of the headsets 125A-D will now bedescribed. It is desirable for the headset to operate safely within themagnetic field of the MR scanner. Therefore, in the present exampleimplementation, the materials forming at least the headsets 125A-Bresiding within the Faraday cage are non-ferromagnetic. In particular,the headsets 125A-B do not use conventional magnetic speakers, normagnetic microphones; instead, they use piezoelectric speakers andpiezoelectric contact microphones.

FIG. 5B is an illustration showing the components of an example headset125A, which includes: at least one noise protection cavity 200 which fitover each ear of the user, at least one piezoelectric speaker 205located inside one or each of the protection cavities for outputtingaudio signals to the user; at least one piezoelectric contact microphone210 for receiving audio input signals from the user; and, headsetcontrol circuit 215 (including but not limited to at least onemicroprocessor); at least one conductor 211 connecting contactmicrophone 210 to the electronic components, at least one battery 216,at least one antenna 220. Headset 125A may include an electrical cable225 for programming and facilitating the operation of the previouslydescribed components of headset 125A.

Although the wireless communication devices employed in the precedingexample embodiments are audio communications devices, it will beunderstood that these example implementation are intended to benon-limiting, and that a wide variety of wireless devices can beemployed according to the present disclosure. For example, any one ormore of the wireless communications device may be a mobile computingdevice equipped with a wireless transceiver, such as, but not limitedto, a smartphone, laptop or tablet computing device. Moreover, thesignals that are transmitted among the wireless communications devicemay be employed to encode various different types of communications,including, but not limited to, audio, text or email messages, data, andvideo.

Although many of the preceding example embodiments describedconfigurations in which the uncompromised longitudinal portion of thewaveguide lies on the magnet room side of the waveguide port, and thecompromised longitudinal portion of the waveguide port lies on thecontrol room side of the waveguide port, it will be understood thatthese are merely example configurations. In other exampleconfigurations, the uncompromised longitudinal portion of the waveguidemay be adjacent to the control room side of the waveguide port, and thecompromised longitudinal portion of the waveguide port may be adjacentto the magnet room side of the waveguide port.

In another example embodiment, a system may be provided in which thewireless transmission frequency of the wireless communication devices isabove the cutoff frequency of the waveguide port. In such a case, theantenna may be located within the waveguide port at any suitablelocation, without compromising the waveguide port, since TE and/or TMmodes exist in the waveguide for the transmission of wireless signals.For example, the example embodiment shown in FIG. 2 may be modified,when the wireless frequency is above the waveguide port cutofffrequency, by ensuring that any external conductors of the wirelessbridge device 150 are in electrical contact with the waveguide port,thus preserving the operation of the waveguide port as a high-passfilter. It is noted that such embodiments are different from thosedisclosed in Patent Cooperation Treaty Patent Application No.PCT/CA2014/050086 because none of the embodiments disclosed by PatentCooperation Treaty Patent Application No. PCT/CA2014/050086 involve theuse of an antenna to transmit and receive wireless signals both insideof, and outside of, the Faraday cage.

The specific embodiments described above have been shown by way ofexample, and it should be understood that these embodiments may besusceptible to various modifications and alternative forms. It should befurther understood that the claims are not intended to be limited to theparticular forms disclosed, but rather to cover all modifications,equivalents, and alternatives falling within the spirit and scope ofthis disclosure.

Therefore what is claimed is:
 1. A wireless communication system forcommunicating through a waveguide port of a Faraday cage, the wirelesscommunications system comprising: one or more internal wirelesscommunication devices located within the Faraday cage, and one or moreexternal wireless communication devices located external to the Faradaycage, wherein said one or more internal wireless communication devicesand said one or more external wireless communication devices areconfigured for wireless communication within a frequency band that lies,at least in part, below a cutoff frequency of said waveguide port; and awireless bridge device comprising an antenna and a transceiver operablyconnected to said antenna, wherein at least a portion of said wirelessbridge device is housed within said waveguide port, such that saidantenna resides within said waveguide port; wherein a conductive path isprovided within a first longitudinal portion of said waveguide port,wherein said first longitudinal portion extends between a first side ofsaid waveguide port and an intermediate location within said waveguideport, and wherein said conductive path is unshielded and resides withinsaid first longitudinal portion without making electrical contact withsaid Faraday cage, such that the propagation of electromagnetic waves issupported within said first longitudinal portion of said waveguide port,and wherein a second longitudinal portion of said waveguide port isabsent of said conductive path, said second longitudinal portionextending between said intermediate location and a second side of saidwaveguide port, such that electromagnetic waves having a frequency belowthe cutoff frequency are attenuated within said second longitudinalportion, thereby preserving the functionality of said waveguide port asa high-pass filter; and wherein said antenna resides within saidwaveguide port at an antenna location that is sufficiently close to saidsecond side of said waveguide port to support the transmission andreception of wireless signals to and from said one or more internalwireless communication devices, and wherein said first longitudinalportion is of sufficiently length to support the transmission andreception of wireless signals to and from said one or more externalwireless communications devices.
 2. The wireless communications systemof claim 1 wherein said antenna is located such that a propagation losswithin said waveguide port, from said antenna to said first side of saidwaveguide port or to said second side of said waveguide port, is lessthan 3 dB.
 3. The wireless communications system of claim 1 wherein saidantenna is located such that the signal-to-noise ratio associated withsignals received from said one or more internal wireless communicationdevices and said one or more external wireless communication devices isat least 3 dB.
 4. The wireless communications system of claim 1 whereinsaid waveguide port has a circular cross-sectional profile, and whereina diameter of said circular cross-sectional profile is less than threeinches, and when said antenna location is less than or equal to 10 cmfrom said second side of said waveguide port.
 5. The wirelesscommunications system of any one of claims 1 to 4 wherein said antennais located such that propagation loss through a portion of the waveguideport on one side of said antenna location and propagation loss throughanother portion of the waveguide port on the other side of said antennalocation is less than 3 dB.
 6. The wireless communications system of anyone of claims 1 to 5 wherein said antenna location is within said firstlongitudinal portion.
 7. The wireless communications system of any oneof claims 1 to 5 wherein said antenna location is within said secondlongitudinal portion.
 8. The wireless communications system according toclaim 7 wherein said antenna location is approximately in the center ofthe second longitudinal portion.
 9. The wireless communications systemaccording to any one of claims 1 to 8 wherein said conductive path isformed, at least in part, by a conductive rod or an outer conductor of acoaxial cable.
 10. The wireless communications system according to anyone of claims 1 to 8 wherein said conductive path is formed, at least inpart, by a power cable providing power to said transceiver.
 11. Thewireless communications system according to any one of claims 1 to 8wherein said conductive path is formed, at least in part, by aconductive path formed by at least in part by a conductive portion of ahousing that houses at least said transceiver, and wherein said housingis configured such that said conductive portion is prevented from makingelectrical contact with said waveguide port when said housing is placedwithin said waveguide port.
 12. The wireless communications systemaccording to any one of claims 1 to 8 wherein said transceiver islocated outside of said waveguide port.
 13. The wireless communicationssystem according to any one of claims 1 to 12 wherein said wirelessbridge device comprises one or more additional antennae.
 14. Thewireless communications system according to any one of claims 1 to 13wherein said wireless bridge device comprises one or more additionaltransceivers.
 15. A wireless communication system for communicatingthrough a waveguide port of a Faraday cage, the wireless communicationssystem comprising: one or more internal wireless communication deviceslocated within the Faraday cage, and one or more external wirelesscommunication devices located external to the Faraday cage, wherein saidone or more internal wireless communication devices and said one or moreexternal wireless communication devices are configured for wirelesscommunication within a frequency band that lies above a cutoff frequencyof said waveguide port; and a wireless bridge device comprising anantenna and a transceiver operably connected to said antenna, wherein atleast a portion of said wireless bridge device is housed within saidwaveguide port, such that said antenna resides within said waveguideport; wherein said antenna resides within said waveguide port at anantenna location that is suitable for to support the transmission andreception of wireless signals to and from said one or more internalwireless communication devices and to and from said one or more externalwireless communications devices.
 16. A wireless communication system forcommunicating through a waveguide port of a Faraday cage, the wirelesscommunications system comprising: one or more internal wirelesscommunication devices located within the Faraday cage, and one or moreexternal wireless communication devices located external to the Faradaycage; and a wireless bridge device comprising an antenna and atransceiver operably connected to said antenna, wherein at least aportion of said wireless bridge device is housed within said waveguideport, such that said antenna resides within said waveguide port; whereina conductive path is provided within a first longitudinal portion ofsaid waveguide port, wherein said first longitudinal portion extendsbetween a first side of said waveguide port and an intermediate locationwithin said waveguide port, and wherein said conductive path isunshielded and resides within said first longitudinal portion withoutmaking electrical contact with said Faraday cage, such that thepropagation of electromagnetic waves is supported within said firstlongitudinal portion of said waveguide port, and wherein a secondlongitudinal portion of said waveguide port is absent of said conductivepath, said second longitudinal portion extending between saidintermediate location and a second side of said waveguide port, suchthat electromagnetic waves having a frequency below a cutoff frequencyof said waveguide port are attenuated within said second longitudinalportion, thereby preserving the functionality of said waveguide port asa high-pass filter; and wherein said antenna resides within saidwaveguide port at an antenna location that is sufficiently close to saidsecond side of said waveguide port to support the transmission andreception of wireless signals to and from said one or more internalwireless communication devices, and wherein said first longitudinalportion is of sufficient length to support the transmission andreception of wireless signals to and from said one or more externalwireless communications devices.